Many types of electronic imaging devices employ some manner of focusing device for focusing light on a desired region. For example, cameras and medical imaging devices may employ a focusing device. The focusing device operates to focus light, typically light from a subject onto some manner of light sensitive surface, such as film or an electronic sensor.
In the prior art, focusing typically relies on a lens arrangement that includes two or more lenses. The lens arrangement may achieve a variable focus distance by mechanically moving one lens with respect to another.
The prior art light focusing method has several drawbacks. Optical refractive lenses are heavy and large. A variable focus lens incorporating two or more lenses therefore is even larger and heavier. Furthermore, a mechanical variable lens apparatus that moves one or more lenses requires a lot of electrical power to operate. Moreover, a mechanical variable lens apparatus is subject to dirt and wear with the resulting loss of reliability.
Therefore, there remains a need in the art for improved light focusing devices.